[Field of the Invention]

The present invention relates to new molecules exhibiting dual emission properties, and more particularly white light emission properties, and their method of preparation.

The present invention also concerns their applications, notably as fluorescent probes in ratiometric detection, or white light emitting sources.

[Background of the Invention]

Fluorescent probes are typically used for qualitative and/or quantitative titrations in various fields such as immunology, molecular biology, medical diagnostic ... An ideal condition for a compound to be used as fluorescent probe, and thus allow the titration of a target analyte, is to display dual emission properties varying depending upon the conditions (presence or not of the analyte, pH ...). Such compounds allow, for example, ratiometric titrations leading to the determination of the analyte concentration, whatever the fluorescent probe concentration.

In the field of luminescent devices, the use of compounds having dual emission properties can lead to the production of polychromatic fluorescence such as white light, without requiring several polychromatic emitters.

Only few systems using a single molecule are known to exhibit dual emission.

However, dual emission, and more particularly white light emission, from a single molecule is an important chemical target because of the possibility of innovative applications to new classes of displays and light sources, such as low-cost, large-area flat-panel displays. Most of the white organic light-emitting devices (WOLEDs) reported so far relied on the use of a combination of several organic components that emit different colors of light (e.g. red/blue/green luminophores) to cover the visible range from 400 to 700 nm.

Therefore, the search for new molecules that can exhibit dual emission properties, and more particularly white light emission properties, is of obvious interest and importance.

[Aim of the Invention]

One aim of the present invention is to provide new compounds with dual emission properties, more particularly in solution and/or in solid state.

Another aim of the present invention is to provide new white light emitting compounds. One aim of the present invention is to provide new compounds displaying broad and tunable dual emission.

The present invention also aims to provide such compounds with good luminescent properties, such as fluorescent or electroluminescent properties.

The present invention aims to provide such compounds with acceptable quantum yields.

The present invention also aims to provide devices for ratiometric detection.

The present invention also aims to provide devices emitting white light. [Description of the Invention]

The present invention concerns a compound of formula (I):

wherein:

A represents an electron-withdrawing group;

D represents an electron-donating group;

X is selected from the group consisting of: O, S and NR, wherein R is selected from the group consisting of: H, an alkyl group preferably comprising from 1 to 20 carbon atoms, an aryl group preferably comprising from 6 to 22 carbon atoms, and a heteroaryl group;

n is an integer from 1 to 4;

m is an integer from 1 to 6, preferably from 1 to 4;

represents a condensed bicyclic aromatic radical comprising from 6 to 22 carbon atoms, and optionally from 1 to 3 heteroatom(s) selected from the group consisting of: N, S and O;

the OH roup being in ortho position of the condensed bicyclic aromatic radical relative to radical.

The present invention concerns a compound of formula (I): wherein:

- A represents an electron-withdrawing group;

D represents an electron-donating group;

X is selected from the group consisting of: O, S and NR, wherein R is selected from the group consisting of: H, an alkyl group preferably comprising from 1 to 20 carbon atoms, an aryl group preferably comprising from 6 to 22 carbon atoms, and a heteroaryl group;

n is an integer from 1 to 4;

m is an integer from 1 to 6, preferably from 1 to 4;

represents a condensed bicyclic aromatic radical comprising from 6 to 22 carbon atoms, and from 1 to 3 heteroatom(s) selected from the group consisting of: N, S and O;

the OH roup being in ortho position of the condensed bicyclic aromatic radical relative to radical.

In one embodiment, in the compound of formula (I):

In one embodiment, the compound of formula (I) is not the following compound:

In one particular embodiment, in the formula (I) above-mentioned, X is O.

In one particular embodiment, in the formula (I) above-mentioned, X is NH.

In one particular embodiment, in the formula (I) above-mentioned, X is NR, wherein

R is an alkyl group preferably comprising from 1 to 20 carbon atoms.

In one particular embodiment, in the formula (I) above-mentioned, X is NR, wherein R is an aryl group preferably comprising from 6 to 22 carbon atoms.

In one particular embodiment, in the formula (I) above-mentioned, X is NR, wherein R is a heteroaryl group preferably comprising from 6 to 22 atoms.

In one particular embodiment, in the formula (I) above-mentioned, X is S.

In one embodiment, in the formula (I) above-mentioned, represents a condensed bicyclic aromatic radical comprising from 6 to 22 carbon atoms, preferably 8 carbon atoms, and 1 heteroatom selected from the group consisting of: N, S and O, preferably O.

In particular, in the formula (I) above-mentioned, represents a condensed bicyclic aromatic radical comprising from 6 to 22 carbon atoms, preferably 8 carbon atoms, and 1 heteroatom selected from the group consisting of: S and O.

In particular, represents

In one embodiment, in the formula (I) above-mentioned, n is 1 or 2.

In one embodiment, in the formula (I) above-mentioned, m is 1 or 2. For sake of clarity, electron-withdrawing group A is not an alkyl group, such as for example tertio-butyl. Thus, compounds 9 and 10 disclosed in Massue et al., "Fluorescent 2-(2'-hydroxybenzofuran)benzoxazole borate complexes: synthesis, optical properties and theoretical calculations",Tetrahedron Letters, 2014, 55, 4136-41 -40" do not fall within the compounds of formula (I) of the present invention.

In one embodiment, the electron-donating group D is selected from the group consisting of:

- 0- ;

- OR _a , wherein R _a is H or an alkyl group preferably comprising from 1 to 20 carbon atoms, in particular OMe;

- NR _b R _c , wherein R _b and R _c are, independently of each other, selected from the group consisting of:

o H;

o alkyl group preferably comprising from 1 to 20 carbon atoms, preferably from 1 to 4 carbon atoms; and

o aryl group preferably comprising from 6 to 22 carbon atoms, preferably a phenyl group;

- NHC(0)R _d , wherein R _d is selected from the group consisting of:

o alkyl group preferably comprising from 1 to 20 carbon atoms preferably from 1 to 4 carbon atoms; and

o aryl group preferably comprising from 6 to 22 carbon atoms, preferably a phenyl group;

- an aryl group preferably comprising from 6 to 22 carbon atoms, preferably a phenyl group; and

- an alkyl group preferably comprising from 1 to 20 carbon atoms;

said alkyl and aryl groups being optionally substituted with at least one electron-donating group, preferably selected from: O ^" , OR _a , NR _b R _c and -NHC(0)R _d , R _a , Rb, R _c and R _d being as defined according to the present invention.

In one embodiment, the electron-donating group D is selected from the group consisting of:

- 0- ;

- OR _a , wherein R _a is H or an alkyl group preferably comprising from 1 to 20 carbon atoms;

- NHC(0)R _d , wherein R _d is selected from the group consisting of: o alkyl group preferably comprising from 1 to 20 carbon atoms preferably from 1 to 4 carbon atoms; and

o aryl group preferably comprising from 6 to 22 carbon atoms, preferably a phenyl group;

- an aryl group preferably comprising from 6 to 22 carbon atoms, preferably a phenyl group; and

- an alkyl group preferably comprising from 1 to 20 carbon atoms;

said alkyl and aryl groups being optionally substituted with at least one electron-donating group, preferably selected from: O ^" , OR _a , NR _b R _c and -NHC(0)R _d , R _a , R _b , R _c and R _d being as defined according to the present invention.

In one embodiment, the electron-donating group D comprises a π-electron conjugated chain comprising for example one or several alkynyl or alkenyl groups, the conjugation being possible by means of alternating alkenylene or alkynylene groups. Such π-electron conjugated chain allows the delocalization of π-electrons across all the adjacent aligned p-orbitals. The presence of such π-electron conjugated chain inside the group D does not change the electron-donating feature of said group D.

For example, an electron-donating group D comprising a π-electron conjugated

chain may be:

In one embodiment, the electron-donating group D is an aryl group comprising from 6 to 22 carbon atoms, preferably a phenyl group, optionally substituted with at least one electron-donating group preferably selected from: O ^" , OR _a , NR _b R _c and -NHC(0)R _d , R _a , R _b , R _c and R _d being as defined according to the present invention.

In one embodiment, the electron-donatin group D has the following formula (A): wherein Y is selected from: O ^" , OR _a , NR _b R _c and -NHC(0)R _d , R _a , R _b , R _c and R _d being as defined above.

In particular, the electron-donating group D is: In particular, the electron-donatin group D is:

In one embodiment, the electron-donating group D has the following formula (B):

wherein Y _{1 ;} Y ₂ and Y ₃ represent, independently of each other, OR _a , R _a being as defined above.

In particular, the electron-donating group D is:

In one embodiment, the electron-withdrawing group A is selected from the group consisting of:

- halogen such as Br, CI, F or I;

- C(0)R _e, R _e being selected from the group consisting of:

o CI;

o H;

o OR _f , R _f being H or an alkyl group preferably comprising from 1 to 20 carbon atoms; and

o an alkyl group preferably comprising from 1 to 20 carbon atoms;

- N0 ₂ ;

- S0 ₂ NR _g R _h , R _g and R _h representing, independently of each other, an alkyl group preferably comprising from 1 to 20 carbon atoms or an aryl group preferably comprising from 6 to 22 carbon atoms;

- CN;

- CF ₃ ;

- alkyl group, preferably comprising from 1 to 20 carbon atoms, substituted with at least one group selected from: halogen such as F, N0 ₂ , CN, C(0)R _e , S0 ₂ NR _g R _h and CF ₃ , wherein R _e, R _g and R _h are as defined above, said alkyl being optionally substituted with a heteroaryl, said heteroaryl being optionally substituted with a substituted heteroaryl ;aryl group, preferably comprising from 6 to 22 carbon atoms, substituted with at least one group selected from: halogen such as F, N0 ₂ , CN, C(0)R _e , S0 ₂ NR _g R _h and CF ₃ , wherein R _e, R _g and R _h are as defined above;

- -S(0) ₂ -W, W being a heteroaryl being optionally substituted with a substituted heteroaryl;

- S0 ₃ H;

- a radical having the following formula : ; and

- N ⁺ RiR _j R _k R|, wherein R,, R , R _k , and R| are, independently of each other, H or an alkyi group preferably comprising from 1 to 20 carbon atoms, said alkyi group being optionally substituted with at least one group selected from: halogen such as F, N0 ₂ , CN, C(0)R _e , S0 ₂ NRgR _h and CF ₃ , wherein R _e, R _g and R _h are as defined above.

In one embodiment, the electron-withdrawing group A is selected from the group consisting of:

- halogen such as Br, CI, F or I;

- C(0)R _e, R _e being selected from the group consisting of:

o CI;

o H;

o OR _f , R _f being H or an alkyi group preferably comprising from 1 to 20 carbon atoms; and

o an alkyi group preferably comprising from 1 to 20 carbon atoms;

- N0 ₂ ;

- S0 ₂ NR _g R _h , R _g and R _h representing, independently of each other, an alkyi group preferably comprising from 1 to 20 carbon atoms or an aryl group preferably comprising from 6 to 22 carbon atoms;

- CN;

- CF ₃ ;

- alkyi group, preferably comprising from 1 to 20 carbon atoms, substituted with at least one group selected from: halogen such as F, N0 ₂ , CN, C(0)R _e , S0 ₂ NR _g R _h and CF ₃ , wherein R _e, R _g and R _h are as defined above;

- aryl group, preferably comprising from 6 to 22 carbon atoms, substituted with at least one group selected from: halogen such as F, N0 ₂ , CN, C(0)R _e , S0 ₂ NR _g R _h and CF ₃ , wherein R _e, R _g and R _h are as defined above;

- S0 ₃ H; and - N ⁺ RiR _j R _k R|, wherein R,, R , R _k , and R| are, independently of each other, H or an alkyl group preferably comprising from 1 to 20 carbon atoms, said alkyl group being optionally substituted with at least one group selected from: halogen such as F, N0 ₂ , CN, C(0)R _e , S0 ₂ NRgR _h and CF ₃ , wherein R _e, R _g and R _h are as defined above.

In one embodiment, the electron-withdrawing group A comprises a π-electron conjugated chain comprising for example one or several alkynyl or alkenyl groups, the conjugation being possible by means of alternating alkenylene or alkynylene groups. Such π-electron conjugated chain allows the derealization of π-electrons across all the adjacent aligned p-orbitals. The presence of such π-electron conjugated chain inside the group A does not change the electron-withdrawing feature of said group A.

For example, an electron-withdrawing group A comprising a π-electron conjugated

chain may be:. or In one embodiment, the electron-withdrawing group A is -C(0)H.

In one embodiment, the electron-withdrawing group A is -C(0)OH.

In one embodiment, the electron-withdrawing group A is -C(0)CI.

In one embodiment, the electron-withdrawing group A is N0 ₂ .

In one embodiment, the electron-withdrawing group A is NH ₄ ⁺ .

In one embodiment, the electron-withdrawing group A is an aryl group comprising from 6 to 22 carbon atoms substituted with at least one nitro group, preferably a phenyl group substituted with at least one nitro group.

In one embodiment, the electron-withdrawing group A is an aryl group comprising from 6 to 22 carbon atoms substituted with at least one fluorine atom, preferably a phenyl group substituted with at least one fluorine atom.

In one particular embodiment, the electron-withdrawing group A is CN.

In one particular embodiment, the electron-withdrawing group A is CF ₃ .

In one particular embodiment, the electron-withdrawing group A is -C(0)OMe.

In one particular embodiment, the electron-withdrawing group A is F.

In one particular embodiment, the electron-withdrawing group A is Br.

In one embodiment, the electron-withdrawing group A is selected from the group consisting of the following radicals:

and

The present invention also relates to a compound of formula

wherein:

- R _{1 ;} R ₂ , R ₃ and R ₄ represent, independently of each other, H or an electron- withdrawing group A;

- R ₅ , R ₆ , R ₇ and R ₈ represent, independently of each other, H or an electron- donating group D;

or R ₅ and R ₆ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising from 4 to 6 atoms, preferably 5 atoms, said cycle comprising at least one heteroatom selected from the group consisting of: N, O and S, and said cycle being optionally substituted by at least one electron-donating group

D;

or R ₆ and R ₇ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising from 4 to 6 atoms, preferably 5 atoms, said cycle comprising at least one heteroatom selected from the group consisting of: N, O and S, and said being optionally substituted by at least one electron-donating group D; or R ₇ and R ₈ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising from 4 to 6 atoms, preferably 5 atoms, said cycle comprising at least one heteroatom selected from the group consisting of: N, O and S, and said being optionally substituted by at least one electron-donating group D; - X, A and D being as defined according to the present invention;

at least one of R ₅ and R _6, or R ₆ and R _7, or R ₇ and R _8, form said at least partially unsaturated cycle;

at least one of R _{1 ;} R ₂ , R ₃ and R ₄ is an electron-withdrawing group A; and

said compound of formula (II) comprising at least one electron-donating group D.

In one embodiment, in the formula (II) above-mentioned, X is O.

In one embodiment, in the formula (II) above-mentioned, X is NH.

In one particular embodiment, in the formula (II) above-mentioned, X is NR, wherein R is an alkyl group preferably comprising from 1 to 20 carbon atoms.

In one particular embodiment, in the formula (II) above-mentioned, X is NR, wherein

R is an aryl group preferably comprising from 6 to 22 carbon atoms.

In one particular embodiment, in the formula (II) above-mentioned, X is NR, wherein R is a heteroaryl group.

In one embodiment, in the formula (II) above-mentioned, X is S.

In one embodiment, in the formula (II) above-mentioned, R ₂ is an electron- withdrawing group A.

In one embodiment, in the formula (II) above-mentioned, Ri , R ₃ and R ₄ are H.

In one embodiment, in the formula (II) above-mentioned, Ri is an electron- withdrawing group A.

In one embodiment, in the formula (II) above-mentioned, R ₄ is Br.

In one embodiment, in the formula (II) above-mentioned, R ₅ and R ₈ are H.

In one embodiment, in the formula (II) above-mentioned, R ₅ and R ₆ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising from 4 to 6 atoms, preferably 5 atoms, said cycle comprising at least one heteroatom selected from the group consisting of: N, O and S, and said being optionally substituted by at least one electron-donating group D. In particular, R ₅ and R ₆ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising 5 atoms, said cycle comprising one oxygen atom and being substituted with one electron-donating group D.

In one embodiment, in the formula (II) above-mentioned, R ₇ and R ₈ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising from 4 to 6 atoms, preferably 5 atoms, said cycle comprising at least one heteroatom selected from the group consisting of: N, O and S, and said being optionally substituted by at least one electron-donating group D. In particular, R ₇ and R ₈ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising 5 atoms, said cycle comprising one oxygen atom and being substituted with one electron-donating group D.

In one embodiment, in the formula (II) above-mentioned, R ₆ and R ₇ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising from 4 to 6 atoms, preferably 5 atoms, said cycle comprising at least one heteroatom selected from the group consisting of: N, O and S, and said being optionally substituted by at least one electron-donating group D. In particular, R ₆ and R ₇ form, together with the carbon atoms carrying them, an at least partially unsaturated cycle comprising 5 atoms, said cycle comprising one oxygen atom and being substituted with one electron-donating group D.

The present invention also relates to a compound having the following formula (III):

wherein:

R ₉ and R ₁₀ represent, independently of each other, H or an electron-donating group D;

R _{1 ;} R ₂ , R ₃ , R _4, R5, Rs, X and D being as defined according to the present invention.

The compound of formula (III) corresponds notably to a compound of formula (II) wherein R ₆ and R ₇ form, together with the carbon atoms carrying them, a furan substituted with R ₉ and R ₁₀ .

In one embodiment, in the formula (III) above-mentioned, X is O.

In one embodiment, in the formula (III) above-mentioned, X is NH.

In one particular embodiment, in the formula (I) above-mentioned, X is NR, wherein R is an alkyl group preferably comprising from 1 to 20 carbon atoms. In one particular embodiment, in the formula (I) above-mentioned, X is NR, wherein R is an aryl group preferably comprising from 6 to 22 carbon atoms.

In one particular embodiment, in the formula (I) above-mentioned, X is NR, wherein R is a heteroaryl group.

In one embodiment, in the formula (III) above-mentioned, X is S.

In one embodiment, in the formula (III) above-mentioned, R ₂ is an electron- withdrawing group A.

In one embodiment, in the formula (III) above-mentioned, is an electron- withdrawing group A.

In one embodiment, in the formula (III) above-mentioned, R ₄ is Br.

In one embodiment, in the formula (III) above-mentioned, R _{1 ;} R ₃ and R ₄ are H.

In one embodiment, in the formula (III) above-mentioned, R ₅ and R ₈ are H.

In one embodiment, in the formula (III) above-mentioned, R ₉ is H.

In one embodiment, in the formula (III) above-mentioned, R ₁₀ is an electron-donating group D as defined according to the invention.

In one embodiment, the compound of formula (III) corresponds to a compound of formula (lll-a) having the following formula:

(lll-a)

, R ₂ , R ₃ , R ₄ , R ₅ , R ₈ , Rg, Ri o and D being as defined according to the invention.

The present invention also relates to a compound having the following formula (IV)

wherein:

Ri i represents H or an electron-donating group D;

R _{1 ;} R ₂ , R ₃ , R ₄ , R5, Rs, X and D being as defined according to the invention. The compound of fo corresponds notably to a compound of formula (III)

wherein R ₉ is H, and R ₁₀ is

In one embodiment, in the formula (IV) above-mentioned, X is O.

In one embodiment, in the formula (IV) above-mentioned, X is NH.

In one particular embodiment, in the formula (IV) above-mentioned, X is NR, wherein R is an alkyl group preferably comprising from 1 to 20 carbon atoms.

In one particular embodiment, in the formula (IV) above-mentioned, X is NR, wherein R is an aryl group preferably comprising from 6 to 22 carbon atoms.

In one particular embodiment, in the formula (IV) above-mentioned, X is NR, wherein R is a heteroaryl group.

In one embodiment, in the formula (IV) above-mentioned, X is S.

In one embodiment, in the formula (IV) above-mentioned, R ₂ is an electron- withdrawing group A as defined according to the invention.

In one embodiment, in the formula (IV) above-mentioned, Ri , R ₃ and R ₄ are H.

In one embodiment, in the formula (IV) above-mentioned, R ₅ and R ₈ are H.

In one embodiment, in the formula (IV) above-mentioned, Rn is an electron-donating group D as defined according to the invention.

The present invention also relates to a compound having the following formula (V):

wherein:

R' and R" represent, independently of each other, H or an alkyl group preferably comprising from 1 to 20 carbon atoms;

R ₃ , R ₅ , R ₈ and X being as defined according to the invention.

The present invention also relates to a compound having the following formula (IV- bis):

wherein:

Ri2, Ri3 and R ₁₄ , independently of each other, represents an electron-donating group D;

R _{1 ;} R ₂ , R ₃ , R ₄ , R5, Rs, and D being as defined according to the invention.

The present invention also relates to a compound having the following formula (IV- bis-1 ):

wherein R _{1 ;} R ₂ , R ₃ , R ₄ , R5, Rs, X and D being as defined according to the invention.

In one embodiment, among the compounds of formulae (I), (II), (III), (IV), (IV-bis), (IV-bis-1 ) and (V), mention may be made to the following ones:

The present invention also relates to the process of preparation of a compound of formula (I) above-mentioned, said process comprising reacting a compound of formula

with a compound of formula (VII):

wherein , A, X, D, n and m are as defined according to the invention.

In one embodiment, the reaction between the compound of formula (VI) and the compound of formula (VII) is carried out in presence of a base, KCN, and a boronic acid, such as for example PhB(OH) ₂ . In a particular embodiment, the reaction is carried out in a polar solvent, such as for example methanol, preferably at room temperature (about 25°C), notably under atmospheric pressure.

In another embodiment, the reaction between the compound of formula (VI) and the compound of formula (VII) is carried out in a polar solvent, such as for example ethanol, under reflux. Then, 2,3-dichloro-5,6-dicyano-1 ,4-benzoquinone is added to the reaction mixture, and the reaction medium was mixed at room temperature (about 25°C).

In one embodiment, in the process above-mentioned, the compound of formula (VI) is a compound of formula (Vl-a):

and the compound of formula (VII) is a compound of formula (Vll-a):

wherein Ri , R ₂ , R ₃ , R ₄ , R5, Rs, Rg, n are as defined according to the invention.

In one embodiment, the compound of formula (Vll-a) results from the reaction of a compound of formula (Vlll-a):

with a compound of formula (IX-a : wherein R ₅ , R ₈ and Rn are as defined above, via a Sonogashira cross-coupling, preferably carried out in presence of Cul, PdCI ₂ (PPh ₃ ) ₂ and a base.

[Definitions]

As used herein, the term "condensed bicyclic aromatic radical" means a radical having two aromatic rings which are fused to each other. Examples of such radical are benzofuran, benzothiophene, indene, purine, isoquinoline, quinoline, indole, napthalene. In particular, the condensed bicyclic aromatic radical is benzofuran.

The charge distribution in a molecule is typically discussed with respect to two interacting effects:

- an inductive effect, which is a function of the electronegativity differences that exist between atoms (and groups); and

- a resonance effect, in which electrons move in a discontinuous fashion between parts of a molecule. Typically, the strength of donor/acceptor couple can be determined by ab initio calculation of density difference between excited state and fundamental state. The common way to define the EDG (electron-donating group) or EWG (electron-withdrawing group) character of a function is to use the couple between the function and the hydrogen (H). The CT (charge transfer) is determined as the distance separating the barycenters of density depletion and gain following the electronic transitions. This CT distance will be correlated to the relative stability of the two tautomeric forms computed as relative free energies.

As used herein, the term "electron-withdrawing group" is also called "electron acceptor" which has its electronic density rising by going from the fundamental state to the excited state. Such term denotes the tendency of a substituent to attract valence electrons from neighboring atoms or atoms on the pi-delocalized system, i.e., the substituent is electronegative with respect to neighboring atoms or atoms on the pi-delocalized system.

As used herein, the term "electron-donating group" is also called "electron donor" which has its electronic density decreasing by going from the fundamental state to the excited state. Such term denotes the tendency of a substituent to provide valence electrons to neighboring atoms or atoms on the π-delocalized system, i.e., the substituent is electropositive with respect to neighboring atoms.

As used herein, the term "alkyl" means a saturated aliphatic hydrocarbon group which may be straight or branched having preferably from 1 to 20 carbon atoms in the chain, optionally comprising at least one unsaturation. Preferred alkyl groups have 1 to 12 carbon atoms in the chain. For example, the alkyl group is a methyl, a propyl, a butyl, a tertiobutyl, a pentyl or an isopropyl. Such alkyl group may include substituents. Said alkyl can also be a cyclic alkyl.

As used herein, the term "aryl" refers to an aromatic monocyclic or bicyclic hydrocarbon ring system having preferably 6 to 22 carbons, more preferably from 6 to 10 carbon atoms. Examples of aryl moieties include, but are not limited to, phenyl, naphthyl, and anthracenyl. In case of electron-attracting group, substituents are preferably selected from the group consisting of those defined previously for group A. In case of electron- donating group, substituents are preferably selected from the group consisting of those defined previously for group D.

As used herein, the term "heteroaryl" refers to an aromatic 5 to 8 membered monocyclic, 8 to 12 membered bicyclic, having 1 to 3 heteroatoms if monocyclic, 1 to 6 heteroatoms if bicyclic, said heteroatoms being selected from O, N, or S. Examples of heteroaryl groups are thiophene, pyridine, furan, pyrolle, benzofuran, benzooxazole. As used herein, the term "substituents" refers to a group "substituted" on an alkyl, aryl, or heteroaryl group at any atom of that group. Suitable substituents include, without limitation, alkyl, alkenyl, alkynyl, alkoxy, halo, ester, hydroxy, cyano, nitro, amino, dialkylamino, S0 ₃ H, perfluoroalkyl, perfluoroalkoxy, amido, sulfonamido, aryl, heteroaryl, heterocyclyl, and cycloalkyl. The preferred substituents on alkyl, aryl or heteroaryl groups are OH, amino, dialkylamino, alkoxy, halo, perfluoroalkyl such as CF ₃ and hereoaryl.

As used herein, the term "alkylene" means a divalent saturated aliphatic hydrocarbon radical, which may be linear or branched, preferably having from 1 to 24 carbon atoms in the chain.

As used herein, the term "alkenylene" means a divalent linear or branched hydrocarbon radical, preferably having 2 to 6 carbon atoms and having at least one double bond, and includes for example ethenylene

As used herein, the term "alkynylene" means a divalent linear or branched hydrocarbon radical, preferably having 2 to 6 carbon atoms and having at least one triple bond. Preferred alkynylene groups include ethynylene (-C≡C-).

As used herein, the term "an at least partially unsaturated cycle" means that the cycle is partially unsaturated or fully unsaturated. Example of fully unsaturated cycle is phenyl. Examples of at least partially unsaturated cycle are furan, thiophene, pyrrole, phenyl, thiazole, imidazole, preferably said cycle being furan. Such aryl group may include substituents.

As used herein, the compounds of formula (I), (II), (III), (IV) or (V) are also called "emitters" or even "organic emitters".

As used herein, the term "dual emission" means that upon photoexcitation, for example at λ _βχ (excitation wavelength) a compound will emit two distinct emission band λ _β ηΕ and _emK corresponding respectively to E ^* and K ^* states. .

As used herein, the term "E ^* " means the enol at its excited state of the compounds according to the invention, having notably the following formula:

As used herein, the term "K ^* " means the keto at its excited state of the compounds according to the invention, having notably the following formula:

As used herein, the term "fluorophore", also called "fluorochrome" or "chromophore", is a fluorescent chemical compound that can re-emit light upon light excitation.

As used herein, the term "protic solvent" means a solvent that include at least one hydrogen atom that is capable of being released in the form of a proton.

As used herein, the term "aprotic solvent" means a solvent that is considered as not being protic. In particular, such solvents are not suitable for releasing a proton or for accepting one. Examples of aprotic solvent are toluene, dimethylformamide, acetone, dimethyl sulfoxide.

As used herein, the term "compound according to the invention", or "compound of the invention" corresponds to a compound of formulae (I), (II), (III), (IV), (V) or their mixtures thereof.

As used herein, the term "transparent" typically means that a person may read alphanumeric characters even the film is placed between said person and said alphanumeric characters.

Reference throughout the specification to "one embodiment", "another embodiment", "an embodiment", and so forth, means that a particular element (e.g., feature, structure, and/or characteristic) described in connection with the embodiment is included in at least one embodiment described herein, and may or may not be present in other embodiments. In addition, it is to be understood that the described elements may be combined in any suitable manner in the various embodiments.

As used herein, the term "dielectric constant of a solvent" is a measure of its polarity. The higher the dielectric constant of a solvent, the more polar it is.

As used herein, the term "conductive polymer" means organic polymers that are able to transport charges (electrons and holes).

As used herein, the term "organic semiconductor polymer" means a polymer of an organic compound capable of exhibiting the properties of a semiconductor.

[Uses]

The present invention also relates to a solution comprising at least one compound according to the invention, and a solvent. Preferably, the solvent is selected from the group consisting of: solvents with low dielectric constant and solvents with high dielectric constant.

In particular, solvents with low dielectric constant are selected from the group consisting of: toluene, cyclohexane, dichloromethane and mixtures thereof.

In particular, solvents with high dielectric constant are selected from the group consisting of: alcohols, dimethylsulphoxide, water, acetone, acetonitrile and mixtures thereof.

The present invention also relates to a solid material (S) comprising, or consisting of, at least one compound according to the invention.

In one embodiment, the solid material (S) consists of at least one compound according to the invention. In this case, the at least one compound according to the invention is in a solid state, such as for example in powder form.

In one specific embodiment, said solid material or compound according to the invention is a crystal, for example a monocrystal.

In one embodiment, the solid material further comprises an inorganic solid for example selected from the group consisting of: KBr matrix pellets, alumine, silica, zeolithe, clays, titanium oxyde and titanium silicium. In particular, the at least one compound according to the invention is combined with or introduced into said inorganic solid.

In particular, the at least one compound according to the invention is dispersed as a solid powder into KBr matrix pellets.

The invention also relates to a material (M) comprising at least one compound according to the invention, and at least one polymer and/or polymeric material and/or an organic matrix, said organic matrix may optionally comprise an inorganic material such as dopants. In one embodiment, the compound(s) according to the invention is(are) encapsulated in said polymer and/or polymeric material and/or organic matrix.

In one embodiment, the material (M) comprises at least one compound according to the invention, and at least one organic matrix.

In one embodiment, the material (M) is an organic semiconductor material.

In one embodiment, the material (M) is a plastic material, especially a transparent plastic material. For example said plastic material is a plastic film, especially a transparent plastic film.

In one embodiment, the material (M) is a conductive plastic.

The present invention thus also relates to a film, especially a transparent film, comprising at least one compound according to the invention.

There is no particular limitation on the method to produce a film. A film according to the invention generally comprises at least one polymer and/or polymeric material, and at least one compound according to the invention. Additional elements may be present in the film, without particular limitation.

According to the invention, the at least one compound according to the invention may be present in the film at various concentrations. Typically the concentration by weight of the at least one compound according to the invention is more than 0.01 % with respect to the weight of the final film (w/w). This concentration may range from 0.05% to 90% (w/w). In one embodiment, the concentration of one or more compounds according to the invention is at least 0.5% (w/w).

Advantageously, the emission spectra of the fluorescent film can be tuned by changing the concentrations of the compound(s) according to the invention in the film. The invention therefore, relates to a dual light emitting film, more particularly to a white-light emitting film.

In one embodiment, the polymer is a conductive polymer.

In one embodiment, the polymer is an organic semiconductor polymer.

In one embodiment, the polymer is selected from the group consisting of: polymers containing acrylate-containing units, for example polyalkylacrylate, polyalkylmethacrylate especially polymethylmethacrylate (PMMA) ; polymers containing siloxane units, for example polyalkylsiloxane, especially polydimethylsiloxane (PDMS), polymers containing hydroxide groups-containing units, for example polyvinyl alcohol (PVA); polystyrene (PS); and any mixture thereof. In particular, the polymer is a mixture of PMMA and PS.

In one embodiment, the polymeric material is cellulose or latex.

A film can be prepared for example from a liquid phase containing at least one polymer and/or polymeric material suitable for forming a film and at least one compound according to the invention. A film may be prepared for example from such a liquid phase by evaporation, preferably slow evaporation, of the liquid phase to yield a film. Solvents of polymer and/or polymeric materials for preparing such a liquid phase are typically organic solvents but may also consist of or contain water. Typically, the liquid phase is a solution containing at least one polymer and/or polymeric material suitable for forming a film and at least one compound according to the invention. The liquid phase may also be a dispersion or an emulsion. Evaporation may be performed for example at room temperature in a container. If needed, the fluorescent film maybe subjected to further solvent elimination. For example the fluorescent film may be dried under vacuum, to remove remaining solvent.

Films can be shaped according to the techniques of the art. The shape of the transparent fluorescent films can be for example controlled by the shape of the container (glass sample tube: cylinder; glass plate substrate: quadrangle). Films can present a very wide range of thicknesses, typically from 10 nanometers (nm) to 1000 micrometers (μηι) or more, preferably from 20 nm to 200 μηι.

In one embodiment, the invention relates to a PMMA/PS film containing at least one compound according to the invention, for example at a concentration ranging from 0.5% (w/w) by weight with respect to the total film weight.

Light emission of the film may be obtained by excitation of the films by a physical stimulus, such as an electromagnetic radiation, typically a light radiation, a magnetic radiation or an electric radiation.

Upon photoexcitation, the inventors advantageously found that the compounds exhibit intense dual emission with contribution from the enol (E ^* ) and the keto (K ^* ) emission, K ^* being formed through excited state intramolecular proton transfer (ESIPT).

The ratio of dual emission intensity R _Du may be defined in the present invention by the ratio between the intensity of the _max (maximum emission wavelength) of the less intense emission band over the intensity of the _max of the more intense emission band. For example, depending of the compound of the invention, the less intense emission band may be the one of the Enol form (E ^* ) or the one of the Keto form (K ^* ).

According to the invention, the compounds of the invention present significant dual emission properties when R _DU is higher than 0.15, preferably higher than 0.2, and more preferably higher than 0.5. In particular, R _DU is higher than 0.8.

Typically, ESIPT is a photophysical process that features a photoinduced proton transfer in the excited-state of specific π-conjugated compounds. The following scheme 1 is a representation of the ESIPT process in the compounds of the invention:

Scheme 1

In particular in ESIPT process, upon absorption of light, a very fast phototautomerization process occurs (in the order of a sub-picosecond timescale) leading either to the sole emission of the tautomer or to a dual emission if the proton transfer is not quantitative. As a result of this sizeable reorganization of the molecular structure upon photoexcitation, large Stokes' shifts may be obtained due to the red-shifted emission of the keto tautomer (K ^* , in the case of a keto-enol tautomerism) as compared to that of the normal enol form (E ).

In particular, the inventors advantageously found that the ratio of emission intensity RDU is tunable. The compounds of the invention advantageously display broad and tunable dual emission.

The compounds according to the invention advantageously display dual emission, and more particularly white light emission, as a single compound in solution and/or in the solid state, and/or when incorporated in a material, such as a polymeric film or a solid material.

More particularly, the inventors found that when the compounds of the invention are in solution, they display dual emission in different type of solvents, such as protic and aprotic solvents. Thus, the compounds according to the invention advantageously exhibit good luminescent properties, such as for example fluorescent or electroluminescent properties.

According to the CIE 1931 XYZ color space, created by the Commission Internationale de I'eclairage (CIE) in 1931 , the CIE chromaticity coordinates for pure white light are (0.33, 0.33).

The compounds according to the invention provide an acceptable quantum yield, which is defined as the quotient of the number of photons emitted divided by the number of photons absorbed. The quantum yield represents the emission efficiency of a given compound.

An acceptable quantum yield is considered to be over 1 .9%, preferably over 5%, and more preferably at least 10%. In particular, the quantum yield of the compounds of the invention is at least 15%.

In one embodiment, when the compounds of the invention are in solid-state, they exhibit a quantum yield higher than 7%, preferably at least 10%, and more preferably at least 20%.

Lifetime (r) is defined as the average length of time for the molecules to decay from one state to another. When a molecule absorbs a photon of appropriate energy, a chain of photophysical events ensues, such as internal conversion, fluorescence, intersystem crossing, and phosphorescence, as shown in the Jablonski diagram. Each of the processes occurs with a certain probability, characterized by decay rate constants (k). Lifetime (r) is reciprocally proportional to the rate of decay: τ = \lk. The lifetime can be considered as a state function because it does not depend on excitation wavelength.

The lifetime of a compound of the invention ranged typically from 0.2 to 10 nanoseconds, more specifically from 0.3 to 5 nanoseconds.

The present invention also relates to a light emitting device comprising at least one compound according to the invention, or a solid material (S) as defined according to the present invention or a material (M) as defined according to the present invention

In one embodiment, the light emitting device is a luminescence device or an electroluminescence device.

Examples of light emitting device are Organic leds (OLEDs).

In one embodiment, the light emitting device is a white light emitting device. Example of such device is WOLED (White organic light emitting diodes).

The present invention also relates to a device for ratiometric analysis comprising at least one compound according to the invention or a solid state material (S) as mentioned above or a material (M) as mentioned above. The ratio of the optical signals (at two distinct wavelengths) may be used to monitor the association equilibrium and to calculate analyte concentrations. Ratiometric measurements eliminate distortions of data caused by photobleaching and variations in probe loading and retention, as well as by instrumental factors such as illumination stability.

The present invention also relates to the use of at least one compound according to the invention, or a solid state material (S) as defined according to the present invention or a material (M) as defined according to the present invention, as fluorescent probe, in particular for ratiometric analysis. The compound according to the invention are thus useful for medical applications.

The present invention also relates to the use of at least one compound according to the invention, or a solid state material (S) as defined according to the present invention or a material (M) as defined according to the present invention, for emitting white light.

The inventors have discovered that the compounds according to the invention, namely compounds of formulae (I), (II), (III), (IV) and (V), and materials comprising them (for example film or solid material), advantageously exhibit dual emitting properties, and more particularly white light emitting properties.

The compounds according to the invention may also be used as pigments or dyes, in particular in paints or textiles, notably for clothes. In particular, the compounds are used in liquid or solid form, such as in powder form.

In one embodiment, the compounds according to the invention are encapsulated, notably in a matrix, such as an organic or polymeric matrix.

In one embodiment, the compounds according to the invention are used as pigment for security inks.

The security inks are well known by the skilled person. Security inks are typically used for security applications such as banknotes, official identity documents (passports, identity cards, birth certificates ...), postage stamps, tax banderoles, security labels and product markings.

Typically, the security inks fulfil the role of security in addition to their coloring function. In particular, the security inks can be used as anti-infringement labelling for different type of products or documents. In this particular case, the labelled product/document may be easily authenticated. In particular, the security inks are used for invisibly print security images having multiple authentication features.

In one embodiment, the present invention relates to security inks comprising at least one compound according to the invention, in particular the compounds being encapsulated such as in a organic or polymeric matrix. Figures

Figure 1 corresponds to the absorption (in grey) and emission spectra (in black) in various solvents for comparative compound 5. Such data were recorded at room temperature (25°C). Only K ^* band appears.

Figure 2 corresponds to the absorption (in grey) and emission spectra (in black) in various solvents for comparative compound 6. Such data were recorded at room temperature (25°C). Only K ^* band appears.

Figure 3 corresponds to the absorption (in grey) and emission spectra (in black) in various solvents for compound 7. Such data were recorded at room temperature (25°C).

Figure 4 corresponds to the absorption (in grey) and emission spectra (in black) in various solvents for compound 8. Such data were recorded at room temperature (25°C).

Figure 5 corresponds to the absorption (in grey) and emission spectra (in black) in various solvents for compound 9. Such data were recorded at room temperature (25°C).

Figure 6 corresponds to the absorption (in grey) and emission spectra (in black) in various solvents for compound 10. Such data were recorded at room temperature (25°C).

Figure 7 corresponds to the solid-state emission spectra of compounds 7 and 8 in KBr pelletsSuch data were recorded at room temperature (25°C).

Figure 8 corresponds to the solid-state emission spectra of compounds 7 to 10 PMMA/PS films . Such data were recorded at room temperature (25°C) using an integration sphere.

The invention is described in the foregoing by way of non-limiting examples.

Examples

The temperature is 25°C, unless contrary indicated.

The pressure is atmospheric pressure (101325 Pa), unless contrary indicated.

General methods and equipment: All reactions were performed under a dry atmosphere of argon using standard Schlenck techniques. Dichloromethane were distilled over P ₂ 0 ₅ under an argon atmosphere. Thin layer chromatography (TLC) was performed on silica gel or aluminium oxide (Al ₂ 0 ₃ ) plates coated with fluorescent indicator. Chromatographic purifications were conducted using 40-63 μηι silica gel. All mixtures of solvents are given in v/v ratio. The 300 ( H), 400 ( H), 75.46 ( ³ C), 100.3 ( ³ C) MHz NMR spectra were recorded at room temperature with perdeuterated solvents with residual protonated solvent signals as internal references. Mass spectra were measured with a ESI-MS mass spectrometer. Electronic absorption and emission spectra were measured under ambient conditions using commercial instruments Shimadzu UV3600 and Horiba Jobin-Yvon Fluoromax 4P. UV-Vis spectra were recorded using a dual-beam grating spectrophotometer with a 1 cm quartz cell. Fluorescence spectra were recorded with a spectrofluorimeter using typical Fluorescence software. Solvents for spectroscopy were spectroscopic grade and were used as received. Standard parameters were used for each instrument used. All fluorescence spectra were corrected from PM response. Luminescence lifetimes were measured on a spectrofluorimeter, using software with time- correlated single photon mode coupled to a Stroboscopic system. The excitation source was a laser diode (λ 320 nm). The instrument response function was determined by using a light-scattering solution (LUDOX). The fluorescence quantum yield (Φ _βχρ ) was calculated from eq (1 ).

I denotes the integral of the corrected emission spectrum, OD is the optical density at the excitation wavelength, and η is the refractive index of the medium. The reference systems used were rhodamine 6G, Φ= 88% in ethanol A _ex = 488 nm for dyes emitting between 480 and 570 nm and quinine sulfate as reference Φ = 0.55 in H ₂ S0 ₄ 1 N, A _ex = 366 nm for dyes emitting below 480 nm.

All chemicals were received from commercial sources (Aldrich, Alfa Aesar or Acros) and used without further purification. 4-(dimethoxy)phenyl acetylene and 4-(di- "butylamino)phenyl acetylene were synthesized according to reported procedures (Feng et al., Org. Lett., 2013, 15, p. 936-939 and Miller et al., Synlett, 2004, 1 , p. 165-168).

A. General procedure for the synthesis of salicylaldehydes (2), (3) and (4)

(1) and Pd(PPh ₃ ) ₂ CI ₂ (5 % molar) were dissolved in THF/triethylamine (3/1 ). The resulting suspension was degassed with argon for 30 minutes before the appropriate 4-substituted phenylacetylene (3 eq.) was added followed by Cul (10 % molar). The resulting mixture was stirred overnight at 60°C. The dark solution was taken up in dichloromethane, washed with water, dried (MgS0 ₄ ) and concentrated in vacuo. The product was purified by silica gel chromatography (CH ₂ CI ₂ /Pet. Ether 1 :1 ) to afford clean salicylaldehyde (2), (3) or (4) after evaporation of the solvents in vacuo. Example 1 : Synthesis of the intermediate 2,4-dihydroxy-5-iodobenzaldehyde (1):

2,4-Dihydroxy-5-iodobenzaldehyde (6g, 43 mmol.) was dissolved in 50 mL of acetic acid. A solution of iodine monochloride (8,46g, 52 mmol.) in 20 mL of acetic acid was added dropwise. The resulting mixture was stirred for 12 h at room temperature before it was poured into a saturated sodium thiosulfate solution (100 mL). The crude solution was extracted four times with ethyl acetate and the solvents were evaporated in vacuo. The crude residue was purified by silica gel chromatography eluting with CH ₂ CI ₂ /Pet. Ether 1 :1 to CH ₂ CI ₂ 100% leading to compound 1 as white/beige powder (4.6 g, 40%). H NMR (300MHz, d ₆ -acetone) δ (ppm): 1 1 .07 (br s, 1 H, OH), 10.73 (br s, 1 H, OH), 9.76 (s, 1 H, OH), 8.05 (s, 1 H, CH Ar), 6.49 (s, 1 H, CH Ar). ³ C NMR (75MHz, d ₆ -acetone) δ (ppm): 195.1 , 164.9, 164.5, 145.7, 1 18.2, 103.1 , 73.2. Example 2: 2-(4-(tert-butyl)phenyl)-6-hydroxybenzofuran-5-carbaldehyde (2)

Beige powder. Yield: 56 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 1 1 .24 (s, 1 H, OH), 9.92 (s, 1 H, CHO), 7.70-7.76 (m, 3H, CH Ar), 7.07 (s, 1 H, CH Ar), 6.92 (s, 1 H, CH Ar), 6.48 (d, 2H, J=8.6Hz, CH Ar), 1 .36 (s, 9H, C(CH ₃ ) ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 190.0, 160.3, 160.0, 157.7, 152.5, 127.0, 126.9, 126.0, 124.8, 123.3, 1 18.3, 100.2, 99.5, 35.0, 31 .4. Anal. Calculated for C ₁₉ H ₁₈ 0 ₃ : C, 77.53; H, 6.16; Found C, 77.37; H, 5.97. EI-MS (m/z): 294.0.

Example 3: 6-hydroxy-2-(4-methoxyphenyl)benzofuran-5-carbaldehyde (3)

Pale yellow powder. Yield: 60 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 1 1 .23 (s, 1 H, OH), 9.92 (s, 1 H, CHO), 6.67-7.76 (m, 3H, CH Ar), 6.97-7.05 (m, 3H, CH Ar), 6.83 (s, 1 H, CH Ar), 3.87 (s, 1 H, CH ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 196.0, 160.6, 160.3, 160.1 , 157.7, 126.6, 123.5, 122.7, 1 18.4, 1 14.6, 99.5, 99.2, 55.6. Anal. Calculated for C ₁₆ H ₁₂ 0 ₄ : C, 71 .64; H, 4.51 ; Found C, 71 .79; H, 4.82. EI-MS (m/z) : 268.0.

Example 4: 2-(4-(dibutylamino)phenyl)-6-hydroxybenzofuran-5-carbaldehyd e (4)

Orange powder. Yield: 44 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 1 1 .24 (s, 1 H, OH), 9.87 (s, 1 H, CHO), 7.57-7.64 (m, 3H, CH Ar), 7.02 (s, 1 H, CH Ar), 6.65-6.69 (m, 3H, CH Ar), 3.32 (m, 4H, J=7.7Hz, CH ₂ ), 1 .56-1 .66 (m, 4H, CH ₂ ), 1 .33-1 .45 (m, 4H, CH ₂ ), 0.99 (t, 6H, J=7.4Hz, CH ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 196.0, 159.9, 158.8, 148.8, 126.4, 125.7, 124.0, 1 17.7, 1 16.4, 1 1 1 .6, 99.1 , 96.7, 50.8, 29.6, 20.5, 14.1 . Anal. Calculated for C ₂₃ H ₂₇ N0 ₃ : C, 75.59; H, 7.45; N, 3.83 ; Found C, 75.34; H, 7.28; N, 3.50. EI-MS (m/z) : 365.2. B. Synthesis of products

Route A: To a solution of 4- ⁱ Bu-2-aminophenol in absolute ethanol was added salicylaldehyde ((2), (3) or (4)) (1 eq.). The mixture was refluxed for 5 h until an orange to red precipitate formed. After cooling down, the precipitate was filtered and redissolved in dry dichloromethane before 2,3-dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ) (1 .2 eq.) was added as a concentrated dichloromethane solution. The resulting dark mixture was stirred at room temperature overnight. After solvent evaporation, the crude residue was purified by silica gel chromatography eluting with CH ₂ CI ₂ /Pet. Ether 1 :1 .

Route B: To a solution of 4-substituted 2-aminophenol in methanol was added the appropriate salicylaldehyde ((2), (3) or (4)) (1 eq.), phenylboronic acid (1 eq.) and potassium cyanide (3 eq.). The resulting mixture was stirred for 12 hours at room temperature before the appearance of a precipitate. After solvent concentration in vacuo, the precipitate was filtered and further washed with EtOH and n-pentane.

Route C: Salicylaldehyde (4), 4-substituted 2-aminophenol (1 equiv), phenylboronic acid (1 equiv) and potassium cyanide (3 equiv) were stirred at room temperature in methanol for 12 hours. The solvents was evaporated in vacuo to dryness and purified on a silica column chromatography, using CH ₂ CI ₂ /Petroleum ether as eluent to afford a the appropriate HBBO dye as a powder. xample 5 (comparative example):

Compound (5) was synthesized through Route A. Light yellow powder. Yield: 34 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 11.76 (br s, 1H, OH), 8.20 (s, 1H, CH Ar), 7.78 (d, 2H, J=8.6Hz, CH Ar), 7.42-7.54 (m, 5H, CH Ar), 7.23 (s, 1H, CH Ar), 6.95 (br s, 1H, CH Ar), 1.42 (s, 3H, -fBu), 1.37 (s, 3H, -fBu). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 158.4, 157.2, 156.8, 152.0, 148.8, 140.0, 127.5, 125.9, 124.7, 123.0, 122.7, 119.1, 115.8, 109.8, 107.7, 100.4, 99.6, 35.2, 34.9, 31.9, 31.4. Anal. Calculated for C ₂₉ H ₂₉ N0 ₃ : C, 79.24; H, 6.65; N, 3.19 ; Found C, 79.04; H, 6.40; N, 2.99. EI-MS (m/z) : 439.1.

Example 6 (comparative example): Compound (6) was synthesized through Route A. Light green powder. Yield: 42 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 11.64 (br s, OH), 8.17 (s, 1H, CH Ar), 7.75-7.78 (m, 3H, CH Ar), 7.52 (d, 1H, J=8.8Hz, CH Ar), 7.41-7.45 (dd, 1H, J=1.8Hz, J'=8.6Hz, CH Ar), 6.97 (d, 2H, J=8.8Hz, CH Ar), 7.21 (s, 1H, CH Ar), 6.84 (s, 1H, CH Ar), 3.86 (s, 3H, CH ₃ ), 1.42 (s, 9H, -fBu). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 163.7, 160.2, 158.3, 157.1, 156.7, 148.8, 147.2, 140.1, 126.4, 123.1, 123.0, 122.9, 118.8, 115.8, 114.4, 109.8, 107.7, 99.5, 99.3, 55.5, 35.2, 31.9. Anal. Calculated for C ₂₆ H ₂₃ N0 ₄ : C, 75.53; H, 5.61; N, 3.39 ; Found C, 75.36; H, 5.37; N, 3.24. EI-MS (m/z) : 413.1.

Example 7: Compound (7) was synthesized through Route B. Brown-yellow powder. Yield: 25 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 11.43 (s, 1H, OH), 8.11 (s, 1H, CH Ar), 7.65 (d, 2H, J=8.9Hz, CH Ar), 7.55-7.51 (dd, 1H, J=4.2Hz, J'=8.9Hz, CH Ar), 7.42-7.39 (dd, 1H, J=2.7Hz, J'=8.3Hz, CH Ar), 7.19 (s, 1H), 7.09 (td, 1H, J=2.7Hz, J=9.0Hz, CH Ar), 6.67- 6.71 (m, 3H, CH Ar), 3.35-3.30 (m, 4H, N-CH ₂ ), 1.66-1.56 (m, 4H, CH ₂ ), 1.44-1.32 (m, 4H, CH ₂ ), 0.98 (t, 6H, J=7.9Hz, CH ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 165.6, 158.5, 158.2, 156.8, 148.6, 145.6, 141.3, 141.1, 126.4, 123.6, 118.2, 117.0, 112.8, 112.4, 111.6, 111.0, 106.8, 105.9, 105.6, 99.5, 97.0, 50.9, 29.6, 20.5, 14.2. Anal. Calculated for C ₂₉ H ₂₉ FN ₂ 0 ₃ : C, 73.71; H, 6.19; N, 5.93 ; Found C, 73.49; H, 5.82; N, 5.64. EI-MS (m/z) : 472.3 (100)

Example 8:

Compound (8) was synthesized through Route B. Yellow powder. Yield: 20 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 11.31 (s, 1H, OH), 8.13 (s, 1H, CH Ar), 8.01 (s, 1H, CH Ar), 7.72-7.63 (m, 4H, CH Ar), 7.20 (1H, s, CH Ar), 6.71-6.67 (m, 3H, CH Ar), 3.35-3.30 (m, 4H, N-CH ₂ ), 1.61 (m, 4H, CH ₂ ), 1.44-1.32 (m, 4H, CH ₂ ), 0.97 (t, 6H, J=7.2Hz, CH ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): Anal. Calculated for C ₃₀ H ₂₉ F ₃ N ₂ O ₃ : C, 68.95; H, 5.59; N, 5.36; Found C, 68.72; H, 5.34; N, 5.27. EI-MS (m/z) : 523.4 (100)

Example 9:

Compound (9) was synthesized through Route B. Brown-yellow powder. Yield: 45 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 11.11 (s, 1H, OH), 8.07 (s, 1H, CH Ar), 7.99 (s, 1H, CH Ar), 7.68-7.62 (m, 4H, CH Ar), 7.17 (s, 1H), 6.68-6.66 (m, 3H, CH Ar), 3.32 (t, 4H, J=7.7Hz, N-CH ₂ ), 1.65-1.57 (m, 4H, CH ₂ ), 1.43-1.34 (m, 4H, CH ₂ ), 0.98 (t, 6H, J=7.3Hz, CH ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 165.9, 158.9, 158.5, 157.0, 151.6, 148.7, 141.0, 129.2, 126.4, 123.9, 123.4, 118.7, 118.4, 116.7, 111.8, 111.6, 109.1, 105.9, 99.6, 96.7, 50.9, 29.6, 20.5, 14.2. Anal. Calculated for C ₃ oH ₂ 9N ₃ 03 : C, 75.13; H, 6.10; N, 8.76 ; Found C, 74.84; H, 5.72; N, 8.54. EI-MS (m/z) : 479.2 (100).

Example 10:

Compound (10) was synthesized through Route B. Yellow powder. Yield: 56 %. H NMR (300MHz, CDCI ₃ ) δ (ppm): 11.39 (s, 1H, OH), 8.39 (s, 1H, CH Ar), 8.13-8.09 (m, 2H, CH Ar), 7.66-7.61 (m, 3H, CH Ar), 7.18 (s, 1H, CH Ar), 6.70-6.66 (m, 3H, CH Ar), 3.96 (s, 3H, OCH ₃ ), 3.34-3.29 (m, 4H, N-CH ₂ ), 1.65-1.55 (m, 4H, CH ₂ ), 1.44-1.32 (m, 4H, CH ₂ ), 0.98 (t, 6H, J=7.2Hz, CH ₃ ). ³ C NMR (75MHz, CDCI ₃ ) δ (ppm): 166.7, 165.1, 158.6, 158.2, 156.8, 152.1, 148.6, 140.5, 127.5, 127.1, 126.4, 123.7, 120.9, 118.3, 116.9, 111.6, 110.4, 106.5, 99.5, 96.9, 50.9, 29.6, 20.5, 14.2. Anal. Calculated for C ₃₁ H ₃₂ N ₂ 0 ₅ : C, 72.64; H, 6.29; N, 5.47; Found C,72.47; H, 6.04; N, 5.22. EI-MS (m/z) : 512.1 (100).

The compounds 7 to 10 incorporate a strongly mesomeric electron-donating p- dibutylaminophenyl as a terminal group on the benzofuran moeity while the benzoxazole moeity is functionalized with several electron-withdrawing groups of increasing electronegativity (F, CF ₃ , CN or C0 ₂ Me for compounds 7, 8, 9 and 10 respectively).

Example 11 :

Compound (11) was synthesized through Route C. H NMR (400 MHz, CDCI ₃ ): δ (ppm) = 12.21 (s, 1H, OH), 8.22 (s, 1H, CH Ar), 7.98 (d, 1H, ³ J= 8.3 Hz, CH Ar), 7.76 (s, 1H, CH Ar), 7.66 (d, 2H, ³ J=9.0 Hz, CH Ar), 7.62 (dd, 1H, ³ J=8.4 Hz, ⁴ J= 1.7 Hz, CH Ar), 7.16 (s, 1 H, CH Ar), 6.72 (d, 2H, ³ J= 8.2 Hz, CH Ar), 6.68 (s, 1 H, CH Ar), 3.34 (t, 4H, ³ J=7.4 Hz, CH ₂ ), 1.67-1.59 (m, 4H, CH ₂ ), 1.47-1.35 (m, 4H, CH ₂ ), 0.99 (t, 6H, ³ J=7.3 Hz, CH ₃ ). ³ C NMR (100 MHz, CDCI ₃ ): δ (ppm) = 172.4, 158.4, 156.5, 152.0, 148.8, 136.2, 129.6 (q, J _C - _F = 33.0 Hz), 126.5, 125.7, 123.9, 123.0, 122.1, 121.8 (q, ³ J _C - _F = 3.7 Hz), 119.5, 119.2 (q, ³ J _C . _F = 3.7 Hz), 117.3, 113.3, 112.0, 99.8, 96.9, 51.1, 29.7, 20.5, 14.1. Anal. Calculated for C ₃ oH ₂₉ F ₃ N ₂ 0 ₂ S: C, 66.90; H, 5.43; N, 5.20. Found C, 66.83; H, 5.69; N, 4.97. EI-MS (m/z (relative intensity)): Theoretical mass 538.19 (100); Found 540.3 (9), 539.3 (28), 538.3 (80), 497.2 (6), 496.2 (21), 495.2 (65), 455.2 (9), 454.2 (27), 453.2 (100), 438.1 (32).

Example 12:

Compound (12) was synthesized through Route C. H NMR (300 MHz, CDCI ₃ ): δ (ppm) = 11.32 (s, 2H, OH), 8.10 (s, 2H, CH Ar), 7.91 (s, 2H, CH Ar), 7.66 (d, 4H, ³ J= 8.9 Hz, CH Ar), 7.59 (d, 2H, ³ J= 8.7 Hz, CH Ar), 7.43 (d,, 2H, ³ J= 9.2 Hz, CH Ar), 7.17 (s, 2H, CH Ar), 6.70-6.67 (m, 6H, CH Ar), 3.32 (t, 8H, ³ J=7.2 Hz, CH ₂ ), 1.67-1.57 (m, 8H, CH ₂ ), 1.46-1.34 (m, 8H, CH ₂ ), 1.00 (t, 12H, ³ J=7.3 Hz, CH ₃ ). ³ C NMR (75 MHz, CDCI ₃ ): δ (ppm) = 165.1, 158.6, 158.3, 156.9, 149.2, 148.7, 140.6, 130.6, 127.3, 126.3, 123.7, 122.6, 121.4, 118.3, 117.0, 11.6, 110.3, 106.6, 99.4, 96.9, 50.9, 29.6, 20.5, 14.1. Anal, calculated for C ₆₁ H ₅ 8F ₆ N ₄ 0 ₆ : C, 69.31 ; H, 5.53; N, 5.30. Anal. Found C, 69.05; H, 5.59; N, 5.23. EI-MS (m/z (relative intensity)): Theoretical mass 1056.43 (100); Found 1056.5 (24), 1013.4 (32), 443.4 (100).

Example 13:

Compound (13) was synthesized through Route C. H NMR (400 MHz, CDCI ₃ ): δ (ppm) = 11.14 (s, 2H, OH), 8.36 (d, 2H, ⁴ J= 1.6 Hz, CH Ar), 8.07 (s, 2H, CH Ar), 8.04 (dd, 2H, ³ J=8.5Hz, ⁴ J= 1.7Hz, CH Ar), 7.71 (d, 2H, ³ J=8.6Hz, CH Ar), 7.64 (d, 4H, ³ J=8.8Hz, CH Ar), 7.17 (s, 2H, CH Ar), 6.68-6.66 (m, 6H, CH Ar), 3.31 (t, 8H, ³ J = 7.3 Hz, CH ₂ ), 1.63-1.56 (m, 8H, CH _2, ), 1.42-1.33 (m, 8H, CH ₂ ), 0.97 (t, 12H, ³ J=7.2 Hz, CH ₃ ). ³ C NMR (100 MHz, CDCI ₃ ): δ (ppm) = 166.1, 158.9, 158.5, 157.0, 151.9, 148.7, 141.2, 139.0, 126.4, 125.0, 123.9, 119.3, 118.4, 116.7, 111.6, 111.5, 106.0, 99.6, 96.8, 50.9, 29.6, 20.5, 14.1. Anal, calculated for C ₅₈ H ₅₈ N ₄ 0 ₈ S.CH ₂ CI ₂ : C, 71.73; H, 6.02; N, 5.77. Anal, found C, 71.56; H, 6.04; N, 5.65. EI-MS (m/z (relative intensity)): Theoretical mass 970.40 (100); Found 972.5 (8), 971.5 (20), 970.5 (30), 928.5 (40), 927.4 (55), 400.8 (100).

Example 14:

Compound (14) was synthesized through Route C. H NMR (400 MHz, CDCI ₃ ): δ (ppm) = 11.36 (s, 1H, OH), 8.10 (s, 1H, CH Ar), 7.86 (s, 1H, CH Ar), 7.66 (d, 2H, ³ J= 8.7 Hz, CH Ar), 7.47 (s, 2H, CH Ar), 7.18 (s, 1H, CH Ar), 6.70 (s, 1 H, CH Ar), 6.68 (d, 2H, ³ J= 8.8 Hz, CH Ar), 3.32 (t, 4H, ³ J= 7.4 Hz, CH ₂ ), 1.64-1.57 (m, 4H, CH ₂ ), 1.43-1.34 (m, 4H, CH ₂ ), 0.98 (t, 6H, ³ J=7.3Hz, CH ₃ ). ³ C NMR (100 MHz, CDCI ₃ ): δ (ppm) = 165.0, 158.6, 158.2, 156.8, 148.6, 148.3, 141.9, 128.1, 126.4, 123.7, 122.1, 118.3, 117.8, 116.9, 111.8, 111.6, 106.6, 99.5, 96.9, 50.9, 29.6, 20.5, 14.2. Anal, calculated for C ₂ 9H ₂₉ BrN ₂ 0 ₃ : C, 65.29; H, 5.48; N, 5.25. Anal. Found C, 65.41; H, 5.49; N, 5.22. EI-MS (m/z (relative intensity)): Theoretical Mass 532.14 (100); Found 535.2 (28), 534.2 (87), 533.2 (29), 532.2 (87), 492.2 (21), 491.2 (76), 490.2 (21), 489.2 (73), 450.1 (25), 449.1 (98), 448.1 (28), 447.1 (100).

Example 15:

Compound (15) was synthesized through Route C. H NMR (300 MHz, CDCI ₃ ): δ (ppm) = 10.97 (s, 1 H, OH), 7.91 (s, 1 H, CH Ar), 7.65 (s, 1 H, CH Ar), 7.56-7.50 (m, 3H, CH Ar), 7.06 (s, 1 H, CH Ar), 6.62 (d, 2H, ³ J= 8.6 Hz, CH Ar), 6.56 (s, 1 H, CH Ar), 3.30 (t, 4H, ³ J=7.2 Hz, CH _2, ), 1.66-1.56 (m, 4H, CH ₂ ), 1.45-1.27 (m, 4H, CH ₂ ), 0.99 (t, 6H, ³ J=7.2 Hz, CH ₃ ). ³ C NMR (75 MHz, CDCI ₃ ): δ (ppm) = 164.8, 158.7, 158.2, 156.8, 148.6, 146.7, 142.0, 130.4, 126.2, 123.7, 121.0, 118.4, 117.9, 116.8, 111.5, 105.8, 103.2, 99.4, 96.7, 50.9, 29.6, 20.5, 14.1 . EI-MS (m/z (relative intensity)): Theoretical mass 610.05 (100); Found 614.1 (47), 612.1 (88), 610.1 (47), 571 .1 (40), 569.1 (80), 567.1 (40), 529.0 (53), 527.0 (100), 525.0 (49). C. Photophysical data

C.1. In solution

Photophysical data in solution in various solvents were collected and are gathered in tables 1 a and 1 b. Table 1 a: Opti l data measured in solution

Compounds Solvent s)

5

360 33500 546 9400 0.05 0.4 cyclohexane

(comparative)

361 37200 550 9500 0.07 0.8 toluene

358 33700 546 9600 0.04 0.5 CH ₂ CI ₂

356 32600 546 9800 0.06 0.3 acetone

6

363 30600 546 9200 0.05 0.6 cyclohexane

(comparative)

364 33100 547 9200 0.06 0.7 toluene

361 32300 549 9500 0.05 0.4 CH ₂ CI ₂

380 32600 ^b /557 8400 0.05 0.4/3.1 acetone

7 387 28200 450/560 3600 0.02/0.05 0.55 3.0/0.7 cyclohexane

389 29900 463/565 4100 0.02/0.08 0.41 3.6/0.7 toluene

386 30100 510/564 6300 0.08 0.83 0.9/4.4 CH ₂ CI ₂

385 29000 500/588 6000 0.02 0.49 0.2/2.3 EtOH

8 391 30200 458/565 3700 0.10 0.69 0.4/0.4 cyclohexane

393 21300 468/568 4100 0.15 0.73 0.6/0.6 toluene

390 27100 522/560 6500 0.20 0.91 1 .3 CH ₂ CI ₂

389 27200 516/588 6300 0.02 0.74 0.3/2.5 EtOH

9 398 29300 463/562 3500 0.03/0.05 0.33 0.5 cyclohexane

396 28000 481/570 4500 0.05/0.05 0.73 0.8/0.8 toluene

10 388 32200 451/562 3600 0.08 0.50 0.3/0.3 cyclohexane 390 32700 467/569 4200 0.12 0.38 0.5/0.5 toluene

389 34700 515/570 6300 0.13 0.80 0.8/5.3 CH ₂ CI ₂

[a] Quantum yields determined in solution, using quinine sulfate as reference Φ = 0.55 in H ₂ S0 ₄ 1 N, A _ex = 366 nm for dyes emitting below 480 nm, Rhodamine 6G Φ = 0.88 in ethanol, A _ex = 488 nm for dyes emitting between 480 and 580 nm. [b] broad shoulder [c] not soluble, [d] R _Du = Intensity of X _max of less intense emission band/Intensity X _max of more intense emission band.

Table 2a : Optical data measured in solution

Compo ^abs ε Δ

4> _f ^a Solvent unds (nm) (M ^"1 .cm ¹ ) (nm) (cm ¹ ) (ns)

12 392 45000 455/567 3500 0.12 0.3/0.4 cyclohexane

394 61400 473/571 4200 0.06 0.6/0.5 toluene

392 62400 507/607 5800 0.03 0.3 EtOH

13 400 67500 478/574 4100 0.14 0.9/0.8 toluene

14 393 35900 453/557 3400 0.10 0.4 cyclohexane

394 32800 473/571 4200 0.09 0.6 toluene

389 13300 515/587 6300 0.03 0.2 EtOH

11 410 14500 485/609 3800 0.02 0.1 cyclohexane

413 25200 489/619 3800 0.01 0.1 toluene

15 402 28200 465/565 3400 0.09 0.6/0.6 cyclohexane

401 27800 481/570 4100 0.13 1 .1/1 .1 toluene

In view of table 1 a, the compounds 5 and 6, which are not compounds according to the invention, do not exhibit dual emission in solution.

On the contrary, compounds according to the invention, namely compounds 7, 8, 9, 10, 1 1 , 12, 13, 14 and 15 exhibit intense dual emission properties, as seen by the presence of two emission bands (A _em ) Such two emissions bands correspond to both the E ^* and the K ^* emissions bands. The intensity of the dual emission was measured with the RDU ratio, which is advantageously higher than 0.2, preferably higher than 0.3.

Such results also indicate that the compounds 7, 8, 9 O, ^{1 1} > ^{1 2} , 13, 14 and 15 display solution dual emissions in various type of solvent, such as for example solvents having low dielectric constant and high dielectric constant.

Compounds 8 and 9 exhibit the most intense dual emission where the maximum wavelength of the two bands E ^* and K ^* are the more strongly separated. The results show that depending on the electronic substitution of the compounds, dual emission (both E ^* and K ^* bands) is observed, whose intensity ratio depends on the electronegativity of the electron-withdrawing group present on the compounds of the invention. This outcome is related to the relative excited state stabilities of the E ^* and K ^* tautomers.

It results from these experiment that the increase of the intensity of the E ^* band can be correlated to the global electronegativity of the fragment attached on the benzoxazole moiety of the compounds: from strongly electron-withdrawing (CF ₃ and CN in compounds 8 and 9 respectively) to mildly electrowithdrawing (F and C0 ₂ Me in compounds 7 and 10 respectively).

Without being bound by theory, it seems that the strong electron-donating ability of the p- dibutylaminophenyl group present on the compounds 7, 8, 9 ,10, 1 1 , 12, 13, 14 and 15, decrease the acidity of the benzofuran-ol moiety of the compounds, increasing its pKa which in turn stabilize the enol isomer in the excited stat. In addition, the presence of electron-withdrawing group on the benzoxazole moiety seems to increase the pKb of said benzoxazole moiety. These combined cooperative effects favor the obtaining of dual emission and alio to tune the R _D u ratio.

In addition, due to the broad emission bands covering most of the visible range, white light emission was observed, notably in cyclohexane, notably for compounds 8, 9 and 10.

C.2. In solid state

Photophysical properties were also investigated in the solid state dispersed in KBr matrix pellets and in PMMA/PS films. The optical properties are presented in tables 2a and 2b. The powders were dispersed in KBr matrix as pellets or dissolved as 0.5% in PMMA/PS and transparent polymer films were prepared on glass plates by spin coating method.

Table 2a: Optical data measured in the solid-state

5

381 535 7600 0.54 0.401 ; 0.577 KBr pellet

(comparative)

360 546 9500 0.29 0.420 ; 0.536 film

6

387 551 7700 0.31 0.465 ; 0.535 KBr pellet

(comparative)

363 544 9200 0.30 0.421 ; 0.540 film

7 400 476/571 0.35 4000 0.10 0.495 ; 0.458 KBr pellet

388 467/563 0.56 4400 0.30 0.386 ; 0.398 film

8 399 501/580 0.60 5100 0.19 0.353 ; 0.479 KBr pellet

399 481/561 0.99 4300 0.22 0.345 ; 0.398 film

395 493/560 0.81 5000 0.32 0.338 ; 0.430 film

10 386 481/564 0.60 5100 0.23 0.387 ;0.418 film

386 481/564 5100 0.23 0.387 ; 0.418 film

[a]R _Du = Intensity of _max of less intense emission band/Intensity _max of more intense emission band [b] Absolute quantum yields determined using an integration sphere.

Table 2b: Optical data measured in the solid-state

Compounds 4> _f ^a CIE Matrices

(nm)

Coordinates

12 463/568 0.37 0.38; 0.38 PS

469/566 0.38 0.36; 0.40 PMMA

13 482/570 0.68 0.32; 0.37 PS

485/569 0.39 0.34; 0.41 PMMA

505/586 0.11 0.37; 0.50 KBr pellet

14 466/570 0.42 0.39; 0.38 PS

465/566 0.33 0.38; 0.42 PMMA

11 525/646 0.22 0.60; 0.38 KBr pellet

15 479/579 0.50 0.31 ;0.36 PS

481/561 0.38 0.34;0.40 PMMA

The emission profiles recorded for compounds 7, 8, 9, 10, 1 1 , 12, 13, 14 and 15 are following the same trends as those observed in the solution-state, i.e. a dual intense emission corresponding to the E ^* and K ^* bands at high and low energies respectively. For the comparative compounds 5 and 6, the emission spectra are quasi-identical as those recorded in solution with the sole K ^* band observed in KBr pellets and thin films of doped polymers respectively.

Besides, the quantum yields for compounds 7, 8, 9 and 10 are significantly higher than those recoded in solution spanning from 10 to 32%.

A more pronounced E ^* emission for compounds 8-9 bearing the strongest attracting groups (CN and CF ₃ for 8 and 9 respectively) was recorded. It was observed that the intensity of the E ^* decreases along with the accepting ability of the group on the benzoxazole side; a feature found both in solution and in the solid-state.

In particular, the results show that as a consequence of the dual emission in the solid-state for compounds 7, 8, 9, 10, 1 1 , 12, 13, 14 and 15, white light emission was observed in PMMA/PS doped films, especially for compound 8 whose CIE coordinates x;y are the closest to pure white (see table 2a).

These experimental results were also analyzed by Time-Dependent Density Functional Theory calculations (TD-DFT) that confirm that, on the one hand, only E ^* and K ^* emissions are present (no rotamer), and, on the other hand, the relative free energies of the two tautomers in the excited state guide the ratio of the E7K ^* emission intensities.

It has been thus discovered that compounds according to the invention exhibit dual emission properties, in solution and/or especially in solid state.

It has been thus discovered that compounds according to the invention provide new white light emitting compounds.

It has been thus discovered that compounds according to the invention display broad and tunable dual emission upon photoexcitation.

It has been thus discovered that compounds according to the invention present good luminescent properties.

It has been thus discovered that compounds according to the invention present acceptable quantum yields.

The compounds according to the invention enable preparing devices for ratiometric detection and devices emitting white light.

D. Theoritical calculations

Theoretical calculations were performed on the following compounds: B1 , B2 and B3. B1 and B2 are comparative compounds, while compound B3 is a compound according to the invention.

The protocol used here is PCM-M06-2X/6-31 G(d), which allows the calculation of the Gibbs relative energies. Such protocol is disclosed in the publication Benelhadj, K. et al., "White emitters by tuning the excited state intramolecular proton transfer fluoresecence emission in 2-(2'-hydroxybenzofuran)benzoxazole dyes", Chemistry a European Journal, 2014, September 21 , 20(40), 1 2843-57.

For B _; the enol conformation is favored by 7 kcal.mol ^"1 in the ground state whereas the keto conformation is favored by 4 kcal.mol ^"1 in the excited state. For B ₂ , the enol conformation is favored by 5 kcal.mol ^"1 in the ground state whereas the keto conformation is favored by 4 kcal.mol ^"1 in the excited state. For B ₃ , the enol conformation is favored by 14 kcal.mol ^"1 in the ground state whereas the keto conformation is favored by 3 kcal.mol ^"1 in the excited state.

The calculated excited-state delta G (eV) give -0.05 for B ₃ which is very likely to display dual emission based on previous experimental/theory analogies.

Bi and B ₂ give -0.10 and -0.1 2 respectively which would be in favored of a single emission (quantitative proton transfer).